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Long-term oxidization and phase transition of InN nanotextures.

Sarantopoulou E, Kollia Z, Dražic G, Kobe S, Antonakakis NS - Nanoscale Res Lett (2011)

Bottom Line: The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed.The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture.When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

No MeSH data available.


Calculated intensity-line profile and d-spacing (homocentric circle) overlaid on the experimental SAED patterns. (a) Cubic bcc In2O3 structure, (b) hexagonal InN structure, (c) tetragonal indium structure, and (d) mixture of 50% InN-50% In2O3.
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Figure 9: Calculated intensity-line profile and d-spacing (homocentric circle) overlaid on the experimental SAED patterns. (a) Cubic bcc In2O3 structure, (b) hexagonal InN structure, (c) tetragonal indium structure, and (d) mixture of 50% InN-50% In2O3.

Mentions: Besides EDXS and EELS, the levels of oxidization of InN films are measured by SAED for different areas of the samples (Figure 9). The diffraction spots are fitted to the hcp-InN and bcc-In2O3 phases (the patterns are taken with 450-nm diameter of the electron beam). Taking into consideration the rotational average of the experimental SAED patterns, the intensity distribution of the diffracted electrons is deconvoluted using Diff Tools scripts in Gatan's Digital Micrograph software. Next, SAED intensity distributions for pure hcp-InN and bcc-In2O3 are calculated using the EMS program code. The best fit between the experimental diffraction patterns and the calculated intensity distributions is obtained by the linear combination approach (sum of weighted parts of both the simulated distributions for InN and In2O3). After an examination of the samples stored for 6 months in ambient conditions, we found approximately equal concentrations of hcp-InN and bcc-In2O3 phases (50% InN(hcp)-50% In2O3(bcc)). The best fit to the experimental patterns is achieved for this concentration, which is in agreement with the EDXS results, where the concentration of oxygen is constantly increasing. When the same sample is stored in isopropanol for the same duration, the best fit is for 80%hcp-InN/20%bcc-In2O3, confirming once more that oxidization takes place after the growth of film from the atmospheric oxygen.


Long-term oxidization and phase transition of InN nanotextures.

Sarantopoulou E, Kollia Z, Dražic G, Kobe S, Antonakakis NS - Nanoscale Res Lett (2011)

Calculated intensity-line profile and d-spacing (homocentric circle) overlaid on the experimental SAED patterns. (a) Cubic bcc In2O3 structure, (b) hexagonal InN structure, (c) tetragonal indium structure, and (d) mixture of 50% InN-50% In2O3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211480&req=5

Figure 9: Calculated intensity-line profile and d-spacing (homocentric circle) overlaid on the experimental SAED patterns. (a) Cubic bcc In2O3 structure, (b) hexagonal InN structure, (c) tetragonal indium structure, and (d) mixture of 50% InN-50% In2O3.
Mentions: Besides EDXS and EELS, the levels of oxidization of InN films are measured by SAED for different areas of the samples (Figure 9). The diffraction spots are fitted to the hcp-InN and bcc-In2O3 phases (the patterns are taken with 450-nm diameter of the electron beam). Taking into consideration the rotational average of the experimental SAED patterns, the intensity distribution of the diffracted electrons is deconvoluted using Diff Tools scripts in Gatan's Digital Micrograph software. Next, SAED intensity distributions for pure hcp-InN and bcc-In2O3 are calculated using the EMS program code. The best fit between the experimental diffraction patterns and the calculated intensity distributions is obtained by the linear combination approach (sum of weighted parts of both the simulated distributions for InN and In2O3). After an examination of the samples stored for 6 months in ambient conditions, we found approximately equal concentrations of hcp-InN and bcc-In2O3 phases (50% InN(hcp)-50% In2O3(bcc)). The best fit to the experimental patterns is achieved for this concentration, which is in agreement with the EDXS results, where the concentration of oxygen is constantly increasing. When the same sample is stored in isopropanol for the same duration, the best fit is for 80%hcp-InN/20%bcc-In2O3, confirming once more that oxidization takes place after the growth of film from the atmospheric oxygen.

Bottom Line: The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed.The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture.When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase.

No MeSH data available.